Vertical cavity surface emitting lasers (VCSEL) include a first distributed Bragg reflector (DBR), also referred to as a mirror stack, formed on top of a substrate by semiconductor manufacturing techniques, an active region formed on top of the first mirror stack, and a second mirror stack formed on top of the active region. The VCSEL is driven by current forced through the active region, typically achieved by providing a first contact on the reverse side of the substrate and a second contact on top of the second mirror stack.
The use of mirror stacks in VCSELs is well established in the art. Typically, mirror stacks are formed of multiple pairs of layers often referred to as mirror pairs. The pairs of layers are formed of a material system generally consisting of two materials having different indices of refraction and being easily lattice matched to the other portions of the VCSEL. For example, a GaAs based VCSEL typically uses an Al.sub.x1 Ga.sub.1-x1 As.backslash.Al.sub.x2 Ga.sub.1-x2 As material system wherein the different refractive index of each layer of a pair is achieved by altering the aluminum content x1 and x2 in the layers. In conventional devices, the number of mirror pairs per stack may range from 20-40 pairs to achieve a high percentage of reflectivity, depending on the difference between the refractive indices of the layers. The large number of pairs increases the percentage of reflected light.
In conventional VCSELs, conventional material systems perform adequately. However, new products are being developed, such as CD write devices and those utilizing infra-red data links, that require VCSELs to operate at a higher power, i.e. greater than 20 milliwatts. For example, in conventional 780 nm and 850 nm VCSELs, which utilize a GaAs substrate, the GaAs substrate is absorptive with a laser emission being toward the opposite direction, the top. Accordingly, heat is dissipated into the GaAs substrate. The GaAs substrate is not a good thermal conductor and thereby causes the heat to accumulate near the active region. This in turn causes a temperature rise which saturates the laser output power. Therefore, it becomes difficult to generate high power from this type of VCSEL, especially at ambient temperatures, i.e. 50-60.degree. C.
Thus, there is a need for developing a reliable, stable and cost effective vertical cavity surface emitting laser (VCSEL) for use in high power operations, that includes smaller thermal resistance through the integration of a heat dissipator, thereby enabling the VCSEL to operate at high power.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art. Accordingly, it is an object of the present invention to provide a new and improved VCSEL for use in high power operations.
Another object of the invention is to provide a reliable high power VCSEL.
And another object of the immediate invention is to provide for an efficient heat dissipator for use in a high power VCSEL.
Still another object of the invention is to provide for a smaller degree of thermal resistance in a high power VCSEL.
Yet another object of the invention is to provide for a highly manufacturable high power VCSEL.